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Biology and Chemistry Research
.05, the cutoff for statistical significance. This means that the terminal bouton numbers of fweDB25, pak3d02472/ fweDB56, Df(3R)pak3 larvae are significantly different than those of fweDB25/fweDB56, indicating that loss of pak3 increases the number of terminal boutons and enhances mutant flower synaptic phenotypes. Figure 2 graphically illustrates this relationship.
Figure 2. Simultaneous pak3 and flower mutations significantly increase terminal bouton numbers: the graph displays the terminal boutons for each genotype. The terminal bouton number of fweDB25, pak3d02472 / fweDB56, Df(3R)pak3 larvae is increased from that of both of the controls. The p-value calculated from Student’s t-test between fweDB25/fweDB56 and fweDB25, pak3d02472 / fweDB56, Df(3R)pak3 is .037, which is statistically significant. Statistical significance is indicated by the (*). For total bouton numbers, the p-value calculated from Student’s t-test between fweDB25/fweDB56 and fweDB25, pak3d02472/ fweDB56, Df(3R)pak3 is 0.054, which is barely above the significance cutoff of 0.05; counting more larvae should increase the statistical power. Thus, it is likely that deleting both pak3 and flower results in different total bouton counts than just deleting flower. Figure 3 offers a graphical representation of terminal bouton numbers for each genotype. Figure 4 provides representative images of NMJ synapses for each genotype. Collectively, the differences in total and terminal bouton numbers indicate that loss of pak3 enhances synaptic phenotypes exhibited by the loss of flower, specifically increasing the extra terminal, and likely total, boutons. Thus, pak3 and flower functionally interact in a positive and synergistic manner, in which the function of both genes is to aid in the proper formation and development of synaptic boutons.
58 | 2013-2014 | Volume 3
Figure 3. Simultaneous pak3 and flower mutations likely affect total bouton numbers: similar to terminal boutons, the average total bouton number of fweDB25, pak3d02472 / fweDB56, Df(3R)pak3 larvae is increased from that of both of the controls. The p-value calculated from Student’s t-test between fweDB25/ fweDB56 and fweDB25, pak3d02472 / fweDB56, Df(3R)pak3 is 0.054, which is barely above the significance cutoff of 0.05. Independent yet interrelated molecular pathways Since loss of pak3 enhances the extra boutons created by loss of flower and increases the severity of the phenotype, pak3 and flower are likely parts of two independent bouton-forming pathways. Removing any one component of a single pathway would disrupt it and likely render the pathway useless (so removing another part would have no additional affect since the pathway has already been disrupted), whereas with multiple signaling pathways, removing parts of both bouton development pathways would cause defects in both, leading to a more severe phenotype than if only one had been disrupted. Additionally, we know that loss of pak3 has little or no effect on bouton number on its own. However, pak3 is a necessary component in bouton formation and may be the only actin-remodeling part of the bouton formation process [15]. Since pak3 is an essential part of the pathway, we would expect its deletion to have a significant impact on the biochemical pathway. However, seeing as loss of pak3 alone has minimal effects on bouton structure, another molecule (likely a molecule that is part of the flower bouton formation pathway) may be able to take over the function of pak3. But, when both pak3 and flower are mutated, both bouton formation pathways are disabled, and there is nothing capable of taking over the actin remodeling function of pak3; as a result, the double-mutant phenotype becomes more severe than that of either the pak3 or flower mutation alone. Thus, although the pak3 and flower pathways leading to bouton formation are separate biochemical pathways, they are highly interrelated and interact with each other in order